The present invention relates to an upper die for fastening a button, and more specifically, to an upper die for use in fastening a button such as a snap button and a decorative button, to a cloth using a button fastener.
When a button such as a male snap button, a female snap button, a decorative button is fastened to a cloth by swaging a post of a button fastener, an upper die is generally used. Such an upper die, as disclosed in e.g. JP,H11-1812,A, is connected to an up-and-down part of a button-fastening press machine. The upper die comprises a die body (swaging punch) having a columnar punch to swage the post of a button fastener, a button-holding member (guide punch) to hold a button at the time of fastening the button, the button-holding member having a center bore to pass the punch therethrough, a cylindrical elastic member disposed between the die body and the button-holding member. When a button is fastened to a fabric, the button is held by the button-holding member of the upper die, a button fastener is set on a lower die, and a cloth is placed horizontally between the button and the button-fastener. After that, the upper die is lowered by operating the button-fastening press machine. By the lowering of the upper die, the post of the button fastener pierces the cloth upward and then passes through a button-fastening opening of the button, and subsequently the post is swaged by the punch of the punch body. At the time of the swaging, the button-holding member pushes the button against the cloth, and the cloth is compressed between the button and the lower die. The elastic member is deformed at the time of the post piercing the cloth by receiving a load in the axial direction from the punch body and the button-holding member, and is also deformed, more than at the cloth-piercing time, at the time of the post being swaged while the cloth is being pressed down. Thereby, the elastic member can help absorb and relieve a load as imposed on the button, the upper die, the button-fastening press machine, etc. at both of the cloth-piercing time and the post-swaging time.
However, the elastic member in a conventional upper die has a single flexibility (spring property) where an amount of deformation increases approximately in proportion to the load in the radial direction. Therefore, to deal with both of the loads at cloth-piercing time and at the post-swaging time, the elastic member can be deformed more than necessary at the swaging by accepting an excess of load, which imposes a high load on the button, the upper die, the button-fastening press machine, etc. If the flexibility of the elastic member is changed in order to reduce the load imposed on the upper die etc. at the swaging, a defect such as buckling of the post would occur at the cloth-piercing time, preventing the post from passing through the cloth smoothly.
[Patent document 1] JP,H11-1812,A
An object of the invention as made in view of such problems as mentioned above is to provide an upper die for fastening a button, which can deal with both of loads as being imposed on an elastic member at cloth-piercing time and at the post-swaging time and can reduce a load as imposed on a button, an upper die, a button-fastening press machine, etc. at the post-swaging time.